The engine control unit (ECU) on a 2004 Nissan Maxima controls all of the engine's electronic components. The ECU also actively monitors a number of sensors within the engine to detect problems and ensure that the engine is operating at its maximum efficiency. When the ECU detects a problem, it stores a trouble code in its memory and illuminates the service engine soon (SES) light. An automotive scan tool is required to reset the Maxima's ECU and turn off the SES light.
Shift the Maxima's transmission into park (automatic) or first gear (manual). Shut off the engine and set the parking brake. Turn the ignition back to the "ON" position but don't start the engine again.
Find the Maxima's diagnostic data port. It is located underneath the dashboard on the driver's side, just above the pedals.
Plug the scan tool's data cable into the Maxima's diagnostic data port and power on the scan tool. Wait for the scan tool to boot up.
Select "ECU" from the tool's main menu, then choose "Codes." Select "Clear all current and stored DTCs." DTC is an acronym for "diagnostic trouble code."
Allow the scan tool to clear the codes from the ECU's memory. Disconnect the scan tool from the diagnostic data port once the display indicates that the codes have been cleared. Start the engine and verify that the SES light is not illuminated. The ECU has been reset.
